Dairy soils are composed of two components, the soil left behind from the milk processing operation and the soil left behind at the end of the cleaning operation. The soil resulting from the milk processing operation can vary widely in composition depending on, for example, the breed of cows, the time of year and the cow's food source. Additionally, if the surface contacting the milk is a heated surface, as used in pasteurization, it may be soiled with certain components in the milk which can be denatured, degraded, caramelized, or concentrated, thereby making soil removal even more difficult.
The second soil results from the interaction between the milk soil residues and the chemicals in the cleaning solution. The problem can be compounded by poor rinsing and poor cleaning of the equipment, resulting in a substantial buildup of residual soil on the surfaces. This can lead to bacterial growth capable of causing a serious health risk when additional milk is processed through the equipment. Also, hardness ions naturally present in the water source used for rinsing or for preparing the concentrate or cleaning solution, can further compound the cleaning problem because of their tendency to react with the cleaning solution and inactivate the builder components of the cleaning solution.
Sodium polyphosphates have been used as the builder of choice in previous aqueous cleaning solutions, but because of the increased use of liquid detergents, where sodium tripolyphosphate has a limited solubility, and increased environmental concerns on the use of phosphorous containing builders, alternative compositions have been investigated. However, with the decrease in phosphate use, performance of the cleaners has also decreased.
U.S. Pat. No. 4,579,676 claims a composition which purportedly avoids a decrease in the cleaning performance of a phosphate free cleaning compositions through the use of a polyacrylic acid in combination with a soil-dispersing amount of a phosphinopolycarboxylic acid. The wash solutions are disclosed to be useful in the cleaning of cleaned-in-place food-processing equipment fouled with greasy or oily soils. However, the composition disclosed in U.S. Pat. No. 4,579,676 continues to use the ecologically undesirable phosphorus in the form of phosphinopolycarboxylic acid.
Another patent, Belgium Patent 762,816, also discloses the use of a reduced amount of phosphorus in a cleaning solution. The solution described contains from 0 to 0.4 wt % of a low level of alkali metal hydroxide, a sequestering agent containing amino and carboxyl groups, from 0.02 to 1 wt. % of condensed phosphate, from 0 to 0.3 wt. % alkali metal silicate and from 0.001 to 0.05 wt. % nonionic surfactant. This composition is supposedly useful for cleaning, with high efficiency and less susceptibility to contamination, heat exchangers used for pasteurizing milk and other dairy and food industry equipment.
A third patent, European Patent 268,873, discloses a cleaning composition based on a quaternary ammonium compound, an alkyl ether carboxylic acid, an alkali metal hydroxide, and a complex-forming amino-polycarboxylic acid. This cleaning composition is purportedly useful for the food industry, especially dairies, does not foam, and also has some disinfectant properties.